Abstract: An apparatus for applying force to a workpiece, the apparatus having a frame with spaced first and second side members and a top frame assembly. An anchor is spaced downwardly from the top frame assembly. There is a force generator connected to the frame assembly. The force generator is operative to apply a force to a workpiece connected between and to the force generator and anchor.

Abstract: A method of offset load testing a tubular composite specimen with two pairs of aligned holes and having at least one defect, the method comprising: providing a testing apparatus having a pair of arms including a fixed arm and a mobile arm; securing the pair of arms using a fastener assembly in each of the two pairs of aligned holes; and moving the mobile arm to impart an offset load force to the tubular specimen. One aspect includes a method of offset load testing comprising: providing a testing apparatus having a pair of arms including a fixed arm and a mobile arm; providing a tubular composite specimen with a top portion and a bottom portion; securing the pair of arms to the top and bottom portions of the tubular composite specimen; and moving the mobile arm to impart an offset load force to the tubular composite specimen.

Abstract: A clamping force visualization device, including a first clamping body (01) for clamping an object; the first clamping body (01) is telescopically assembled on a base (14), an elastic element (110) is provided between the first clamping body (01) and the base (14), and a clamping force scale (11) and a reading indicator (15) are respectively provided on the first clamping body (01) and the base (14); when the first clamping body (01) clamps the object, the elastic element (110) measures a clamping force and the reading indicator (15) points to the clamping force scale (11) for reading, so that the magnitude of the clamping force can be intuitively seen and read during clamping, thereby achieving accurate clamping. A clamp including the clamping force visualization device is also involved.

Abstract: A fixture for masking a gas turbine engine blade, the blade having a root, a platform and an airfoil, the platform having inner and outer surfaces and peripheral faces extending between the surfaces, the fixture including a base with a receptacle for receiving the root of the blade; a removable sidewall mountable to the base to form a masking box with the receptacle that shields the root; a first removable Z plane detail mountable to the base, the first removable Z plane detail providing a first electrical contact point to the root; and a second removable Z plane detail mountable to the removable sidewall, the second removable Z plane detail providing a second electrical contact point to the root

Abstract: A testing system configured to determine at least one physical characteristic of a work piece. The testing system includes an effector frame having an effector interface configured for coupling with a manipulator assembly. The effector frame includes at least one torque sensor. A ballast bracket is configured for coupling between the at least one torque sensor and the work piece. The ballast bracket includes a sensor interface coupled with the at least one torque sensor, and at least one work piece latch configured for coupling with the work piece. A movable ballast assembly is coupled with the ballast bracket, and includes a counter ballast movably coupled with the ballast bracket and movable relative to the at least one torque sensor. A ballast actuator coupled with the counter ballast is configured to move the counter ballast relative to the at least one torque sensor.

Abstract: Disclosed are a tube pure shear loading device and method. A first mandrel penetrates into a first half tube, and a second mandrel penetrates into a second half tube. The size of the first mandrel matches the size of the first half tube, and the size of the second mandrel matches the size of the second half tube. A first connecting portion of the first mandrel and a second connecting portion of the second mandrel are loaded, and a first protruding portion and a second protruding portion transmit a force to a to-be-tested tube, so that a material of a whole tube in the same plane as a right plane or a left plane of the first half tube and a left plane or a right plane of the second half tube is in a pure shear stress state.

Abstract: A test fixture configured to attach to and apply a tensile force to a test specimen. The test fixture may include a first clevis section and a second clevis section that are each configured to be attached to the test specimen. Each of the first and second clevis sections may include a fixed block and a movable block. Connectors connect the clevis sections together and hold the test specimen. The first and second clevis sections may be moved apart to apply a force to the attached test specimen to test one or more properties of the test specimen.

Abstract: A site-specific customizable nacelle for a wind turbine includes a plurality of walls arranged together to form an inner volume. The walls include a base wall, side walls, a front wall, a rear wall, and a top wall. Each of the walls is constructed of one or more outer skin layers positioned adjacent to one or more inner skin layers and infused together via a resin material. Further, the nacelle includes a plurality of reinforcement members secured to one or more of the plurality of walls on an interior side or an exterior side of at least one of the one or more outer skin layers or the one or more inner skin layers at locations requiring additional reinforcement. As such, the reinforcement members can be tailored according to a particular wind turbine site.

Abstract: A method for testing for hydrogen embrittlement, including mounting a container around a steel alloy test specimen, the container having a closed bottom below a notched area on the test specimen and an open upper end above the notched area; applying a tensile load to the test specimen and sustaining the load for a selected duration to incubate potential hydrogen embrittlement cracks with a sub-critical flaw size if sufficient hydrogen in dangerous levels is present in the test specimen; then, while sustaining the load, dispensing a cryogenic fluid into the container, immersing and chilling the notched area, reducing the sub-critical flaw size for any hydrogen embrittlement cracks incubated; and with the sustained load, fracturing the notched area if the sub-critical flaw size of any hydrogen embrittlement cracks incubated reaches a critical flaw size.

Abstract: Test rig for a back-to-back test of a turbine, including an axle supported in at least one bearing fixed to a carrier, a gear coupled to the axle and a motor coupled to the gear, whereby a gear bearing arrangement comprising two radially extending arms to be coupled to the gear and extending in opposite directions, which arms are pivotally connected to a pair of torque arms extending in a basically parallel direction, with the ends of the torque arms being pivotally coupled to a frame including lateral extensions extending in opposite directions with connection segments, to which segments respective second torque arms arranged in a basically vertical direction in respect to the pair of torque arms are pivotally connected, which second torque arms are pivotally connected to a respective connection element arranged at the carrier.

Abstract: A molding monitoring apparatus acquires an image of a molding molded by an injection molding machine, determines whether abnormality is present in the molding, and specifies an abnormality occurrence position thereof when the abnormality is present. Further, the molding monitoring apparatus calculates the number of abnormality occurrences for each abnormality occurrence position, and compares, among the calculated number of abnormality occurrences for each abnormality occurrence position, the number of abnormality occurrences for each abnormality occurrence position in a certain term with the number of abnormality occurrences for each abnormality occurrence position in another term.

Abstract: The invention relates to a test bench (1) for testing a drive train of a wind turbine, comprising a drive device (40) for introducing test power into the drive train, which can be detachably connected to a drive train to be tested. The invention further relates to a method for testing a drive train of a wind turbine by way of a test bench (1), and to a drive train of a wind turbine. The test bench (1) according to the invention is characterized in that the drive device (40) for testing a drive train is or will be fitted and mounted on or to the drive train so as to be removable, wherein most of the weight of the drive device (40) is borne by the drive train when the drive device (40) is fitted or mounted.

Abstract: An electrically powered cycle comprising a detachable battery mounted by sliding on two rails of a battery receptacle located on the central portion of the handlebar. The rails are inclined downward and rearward and the battery is inserted into the receptacle by sliding the battery from the upper front end of the rails. The battery is facing the user and visible to the user. The rails also serve to connect the battery electrically.

Abstract: Wrinkling of thin films is a strain-driven process that enables scalable and low-cost fabrication of periodic micro and nano scale patterns. However, real-world application is limited by the inability of current tools to provide the means for applying large, accurate, and non-equal biaxial strains via a device that can fit within the vacuum chambers that are required for thin film deposition/growth during wrinkling. The present biaxial tensile stage is a compact system that enables one to apply large and accurate non-equal biaxial strains to elastomeric films. It consists of (i) fixtures to clamp and hold films onto the stage, (ii) linear bearings for motion guidance, (iii) integrated actuators for real-time stretch control, (iv) base with kinematic coupling for registration to a metrology system, and (v) the structural frame.

Abstract: A remote control robot system includes a surgical robot having a surgical tool which is used to perform minimally invasive surgery. The surgical tool includes a detection member having a plurality of detection parts, a support member, and an optical fiber disposed between the detection member and support member. A magnitude of force and a distribution of the force may be measured by individually disposing a plurality of optical fiber bragg gratings (FBGs) below the plurality of detection parts, respectively. Accordingly, the surgical robot or the remote control robot system may provide a more precise control function and a hand-touch diagnosis function.

Abstract: A compression fitting includes a housing, a compressible seal, a follower and a driving member. The housing includes an axial cavity having a lateral sidewall that includes an axial keyway therein. The cavity terminates at a first end portion thereof at a seat. The compressible seal may receive a signal transmitting lead therethrough, and is disposed within the cavity and seated on the seat. The follower is axially movable within the cavity for selective engagement with the seal for axially compressing the seal against the seat, the sidewall of the cavity and the signal transmitting lead. The follower includes an integral key that extends laterally outward therefrom and is received within the keyway, and an axial bore for accommodation therewithin of the lead. The driving member is rotatably mounted on the housing and engageable with the follower such that rotation of the driving member causes an axial translation thereof.

Abstract: The strain gauge holder 1 includes a holder body 10 on a side surface of a pipe 3, a gauge pressing member 21 for pressing a strain gauge 2 against the side surface of the pipe, and a feed mechanism for giving a pressing force to the gauge pressing member. The guide grooves 12 guide the gauge pressing members. The feed mechanism feeds the gauge pressing member in the guide groove to press the strain gauge 2 against the side surface of the pipe 3. The feed mechanism includes cylindrical portion 32a, bushing 32, and feed screw 31. Each of the feed screws 31 threadedly inserted into the bushing mounted on the holder body is threadedly inserted to feed the gauge pressing member.

Abstract: A sample holder for receiving a sample includes a sample receiving device for clamping the sample, which is assigned a holding means which has at least two prongs protruding from the sample receiving device for a gripping means. Also disclosed are a receiving device, a sample holder magazine, a sample feeding system, a clamping device and an examining device.

Abstract: Provided is a test jig including a jig main body having, at an end portion thereof, an insertion part into which an electrode lead is inserted and a fixing member detachably coupled to the insertion part to fix the electrode lead inserted to the insertion part, wherein the insertion part includes insertion faces outwardly extending from both end portions of the jig main body, and coupling faces extending from the insertion faces toward insides of the jig main body and brought into contact with the fixing member, and thus a tensile test is performed on an ultrasonic-welded portion of the electrode lead without an additional cell.

Abstract: A load test stand includes a frame, a flange, and a spring mechanism. The spring mechanism is mounted on the frame and includes a symmetrical arrangement of at least four spring elements. The spring mechanism also includes frame points connecting the spring mechanism and the frame and articulation points connecting the spring mechanism and the flange. The flange can be coupled, by an adapter, to the output shaft of a servo system that is to be tested.

Abstract: The test fixture includes a housing, a first grip, and a second grip. The first grip and the second grip are each configured to clamp onto an upper surface and lower surface of a material coupon. The test fixture also includes an upper input jaw and a lower input jaw each configured to clamp onto the material coupon near a center of the upper surface and the lower surface of the material coupon. The test fixture is configured to load the material coupon in a first direction and a second direction. The first grip and the second grip are each configured to clamp onto the material coupon at a location which accordingly results in a desired testing ratio regardless of a variation in thickness of the material coupon.

Abstract: Some embodiments include an apparatus for testing flexible displays. The apparatus can include: (a) a first clamp configured to receive a first end of the flexible display; (b) a second clamp configured to receive a second end of the flexible display, wherein the second end of the flexible display is opposite the first end of the flexible display; and (c) a test column. Other embodiments and methods are disclosed herein.

Abstract: A sample gripping and heating assembly includes an assembly housing and first and second heating grips coupled with the assembly housing. The first and second heating grips each include a gripping surface, and the gripping surfaces of the first and second heating grips are opposed to each other. Each of the first and second heating grips further includes a heating element adjacent to the gripping surface. Optionally, the sample gripping and heating assembly is included in a heating system including a probe heater having a probe heating element for heating of a probe. The heating system is included with a testing assembly having a stage coupled with the sample gripping and heating assembly, and a transducer assembly coupled with the probe heater.

Abstract: A tissue measurement system includes a clamp, a measuring head, and a deflection sensor. The clamp includes a first plate and a second plate releasably engageable with one another to secure a substantially planar biological tissue. In the engaged position, the first and second plates define at least a portion of a test section along which a portion of the secured substantially planar biological tissue is disposed. The measuring head is movable toward the test section and into contact with the portion of the substantially planar biological tissue disposed along the test section. The deflection sensor is responsive to movement of the biological tissue contacted by the measuring head.

Abstract: An axle load monitoring system configured for use on an axle housing is provided. The axle load monitoring system can include a mounting structure and a strain gauge. The mounting structure can have a first end portion, a second end portion and an intermediate portion. The first end portion can be fixedly coupled to the axle housing. The second end portion can be fixedly coupled to the axle housing. The intermediate portion can be offset away from the axle housing. The strain gauge can be fixedly coupled to the mounting structure at the intermediate portion. The strain gauge can be configured to measure strain of the mounting structure.

Abstract: An apparatus for testing an angle between first and second legs of a torsion spring includes a board, a limiting block and a pin sandwiching the first leg, a positioning member positioning a main body of the torsion spring with the limiting block, and a test block including a bottom wall slidably contacting the limiting block, and a first sidewall and a second sidewall. Angles between the bottom wall and the first and second sidewalls are respectively minimal and maximal values that equal 180 degrees subtracted by an angle within a qualified range between the first and second legs. The first and second sidewalls is moved toward the second leg in turn. If a bottom end of the first sidewall and a top end of the second sidewall both can contact the second leg, the angle between the first and second legs is qualified. Otherwise, the angle is unqualified.

Abstract: Provided is a bending test apparatus for flexible substrate which may increase or maximize reliability. The bending test apparatus includes a table, a first electrode part fixing one side of a flexible substrate on the table, a guide rail disposed adjacent to the first electrode part, the guide rail extending from the one side of the flexible substrate to the other side, a slider moved along the guide rail, and a second electrode part connected to the slider, the second electrode part approaching or spacing the other side of the flexible substrate to/from the first electrode part.

Abstract: A load test stand includes a frame, a flange, and a spring mechanism. The spring mechanism is mounted on the frame and includes a symmetrical arrangement of at least four spring elements. The spring mechanism also includes frame points connecting the spring mechanism and the frame and articulation points connecting the spring mechanism and the flange. The flange can be coupled, by an adapter, to the output shaft of a servo system that is to be tested.

Abstract: A cylinder portion is divided into a cylinder main body, and two side cylinders coupled to opposite ends of the cylinder main body. The cylinder main body is configured so that a sample-enclosing capsule in which a sample and a pressure medium are enclosed can be disposed inside the cylinder main body. Pistons for load transmission are disposed at opposite ends of the interior of the cylinder portion; and locking nuts are provided on the outer sides of the positions. The pistons are moved in an axial direction by screwing the locking nuts. With this configuration, a piston cylinder-type high-pressure generating device in which a cylinder having a small outer diameter is formed of a non-magnetic material can generate a high pressure while securing a sample space having a predetermined effective volume.

Abstract: A very versatile testing module includes a main body, a drive module, a sliding module, a transmission module, and a frictional member. The drive module is positioned in the main body. The transmission module includes a rotational plate and a connecting plate. The drive module drives the rotational plate to rotate. One end of the connecting plate attached to the sliding module, and the other end thereof adjustably attached to the rotational plate. The frictional member is mounted to the sliding module.

Abstract: The disclosure relates a safety shield for the jaws of a grip used for tensile or similar materials testing. The safety shield typically attached to the jaws and shields the jaws on two, three or four sides in order to reduce the hazard of a user placing his or her fingers between the jaws while positioning the testing sample or specimen therebetween. A user is typically able to adjust the position of the safety shield to achieve greater safety. The safety shield may be configured from planar material, such as sheet metal or plastic, or from wire material.

Abstract: A sample for fatigue and/or crack growth testing, including an axisymmetric or cylindrical gage section with a concentric hole running from a first end, and terminating within the gage section, with one mode of loading introduced at the terminus of the hole, and reacted at the end where the hole originates. A second mode of loading is optionally introduced at a second end of the specimen. Use of the specimen is described in both in the context of an apparatus for fatigue/crack growth testing described in the referenced parent application, as well as with conventional test machines.

Abstract: A positioning device for positioning a number of two-sided adhesive pieces includes a base, a number of pulling blocks, and a pressing block. The base includes a positioning block defining a number of positioning holes. Each pulling block includes a connecting plate, and a supporting plate protruding out from a top end of the connecting plate. A first surface of each adhesive piece is adhered on a top surface of one of the supporting plate. The connecting plate is received in a corresponding one of the positioning hole. The pressing block is attached to the positioning block. A second surface of each adhesive piece to be adhered to a bottom surface of the pressing block.

Abstract: A sample holder for receiving a sample includes a sample receiving device for clamping the sample, which is assigned a holding means which has at least two prongs protruding from the sample receiving device for a gripping means. Also disclosed are a receiving device, a sample holder magazine, a sample feeding system, a clamping device and an examining device.

Abstract: A method for quasi-static testing a magnetic recording head read sensor is described. The method includes applying a first voltage to a heater in the magnetic recording head and measuring an output of the magnetic recording head read sensor while applying the first voltage to the heater and recording the measured output as a first set of measurements. The method further includes applying a second voltage to the heater in the magnetic recording head and measuring the output of the magnetic recording head read sensor while applying the second voltage to the heater and recording the measured output as a second set of measurements. The first and second sets of measurements are then compared.

Abstract: Disclosed is an apparatus and method for measuring the diametral change in a cylindrical component by monitoring and measuring bending (compression and tension) effected by the diametral change in a plane perpendicular to the diameter of the cylindrical component. The apparatus for effecting the method comprises at least one web, but typically two webs, defining planes perpendicular to the diameter of the cylindrical component and strain measuring elements mounted on the web planes and arranged to sense and measure the compressive and tensile (bending) action of the strain-gauge-mounted webs.

Abstract: Hydraulic section (1) including: a main spool (2);a pressure compensator (40;4) able to maintain a substantially constant pressure drop through a metering orifice (3) of the main spool (2); a first chamber (7) interposed between the main spool (2) and a first end (16a) of the compensator (40;4) and a second chamber (6) situated at a second end (16b) of the compensator (40;4), the second chamber (6) being connectable to a feed line (Pal) from a pump (100) by a predefined channel (Pp) in such a way that said hydraulic section (1) operates as a priority section, and being connectable to a line (LS) for detecting the highest load pressure in such a way that the hydraulic section (1) operates as a flow-sharing section.

Abstract: The invention provides a fatigue exciter for wind turbine blades. Wind turbine blades require excitation at or near their natural frequency to induce bending moments that simulate in service loadings and must be easily controllable and with the minimum of unnecessary added mass or force. The invention provides a device and a method by which force controlled feedback is used for finding an optimal excitation frequency. This force could be provided e.g. by a digital signal generator.

Abstract: A test apparatus configured to test connectors is provided. The test apparatus may include a fixture that holds a first connector and an actuator that holds a mating second connector. The actuator may axially displace the second connector in and out of engagement with the first connector. A compliance mechanism, which may be coupled to the fixture or the actuator, may provide one of the connectors with compliance in order to facilitate alignment of the connectors during engagement and disengagement thereof. The compliance mechanism may allow movement of one of the connectors perpendicularly to the actuation axis and/or angular movement about the actuation axis while preventing axial movement within the compliance mechanism. Accordingly, forces associated with engagement and disengagement of the connectors measured by a load cell may more closely resemble actual forces experienced by a user during use of the connectors.

Abstract: A system (1100) for fatigue testing wind turbine blades (1102) through forced or resonant excitation of the base (1104) of a blade (1102). The system (1100) includes a test stand (1112) and a restoring spring assembly (1120) mounted on the test stand (1112). The restoring spring assembly (1120) includes a primary spring element (1124) that extends outward from the test stand (1112) to a blade mounting plate (1130) configured to receive a base (1104) of blade (1102). During fatigue testing, a supported base (1104) of a blade (1102) may be pivotally mounted to the test stand (1112) via the restoring spring assembly (1120). The system (1100) may include an excitation input assembly (1140) that is interconnected with the blade mounting plate (1130) to selectively apply flapwise, edgewise, and/or pitch excitation forces.

Abstract: A detecting device for performing fatigue tests on a pivoting piece includes a clamping module and an actuating module. The clamping module clamps the pivoting piece. The actuating module includes an elastic actuating shaft abutting the clamping module and a resilient member mounted in the elastic actuating shaft. The resilient member is adapted to push forward against spring pressure and retract by the release of spring tension so as to achieve cyclic movements in the pivoting piece.

Abstract: Disclosed is a local antistress test platform, comprising a test frame and a weight test rod for providing a local stress to a tested panel by adding weights. The local antistress test platform further comprises a movable test hole table for fixing the weight test rod; the movable test hole table is removably jointed to the test frame. The present invention also relates to local antistress test apparatus. The local antistress test platform and the test apparatus can easily locate the antistress test position and be adaptable to panel test for panels of different sizes.

Abstract: A wind turbine gearbox test cell includes a cradle and a base mounted to a first support structure. Load devices are interconnected between the cradle and base and are configured to input at least one of thrust, radial and yaw loads to the gearbox through the cradle to a wind turbine gearbox under test. A controller is in communication with the load devices and is programmed to command the load devices to input the at least one of thrust, radial and yaw loads to the gearbox corresponding to a simulated wind turbine gearbox loading event. The test cell includes dynamometers and gearboxes that can be reconfigured based upon the particular wind turbine gearbox under test.

Abstract: A magnetic suspension supporter for a direct tension test apparatus, includes an upper end cap and a lower end cap for fixing a sample, an upper chain and a lower chain connected to the upper and lower end caps respectively, an upper joint and a lower joint connected to the other ends of the upper and lower chains respectively, the lower joint being fixed to the test machine foundation. In addition, the upper and lower end caps, the upper and lower chains, the upper and lower joints as well as the supporter having a common vertical axis and being arranged in a cascade form, characterized in that a sample supporter is arranged between the lower end cap and the test machine foundation. The sample supporter is composed of a pair of upper magnet provided at the underside of the lower end cap and lower magnet on the upside of the test machine foundation, which constitute two magnets structure. The polarity directions of the two magnets are reversed and the same polarity is arranged oppositely on the axis.

Abstract: In one embodiment, a force sensor apparatus is provided including a tube portion having a plurality of radial ribs and at least one fiber optic strain gauge positioned over each rib of the plurality of radial ribs. The strain gauges are comprised of a negative thermo-optic coefficient optical fiber material in one embodiment. A proximal end of the tube portion is operably couplable to a shaft of a surgical instrument that is operably couplable to a manipulator arm of a robotic surgical system, and a distal end of the tube portion is proximally couplable to a wrist joint coupled to an end effector. In another embodiment, adjacent fiber optic strain gauges with differing thermal responses are used to solve simultaneous equations in strain and temperature to derive strain while rejecting thermal effects. In yet another embodiment, a thermal shunt shell is over an outer surface of the tube portion. An advantageous surgical instrument having improved temperature compensation is also provided.

Abstract: A testing apparatus includes a support mechanism, a pushing device, and a clamping device secured to the driving member. The clamping device secures a product. The pushing device includes a guiding pipe, a driving member moveably attached to the guiding pipe, and an elastic member received in the guiding pipe. The elastic member is connected to a first end of the driving member. The first end of the driving member is received in the guiding pipe. The clamping device is secured to the driving member. Wherein the guiding pipe is adapted to receive air, the driving member is adapted to be driven by air to move along a first direction, and the elastic member is adapted to rebound to pull the driving member to move along a second direction opposite to the first direction.

Abstract: A document handling device has a support frame with four legs, at least one of which is height-adjustable. The support frame includes a torsion meter and a display for displaying a torsion of the support frame. The display is arranged in a position where it is visible for a person adjusting the height of the at least one height-adjustable leg. In an embodiment, it is possible to perform state detection between subsequent droplet ejections, thereby obtaining a highly reliable inkjet process.

Abstract: A tube or pipe clamp incorporates a clamping force measurement device. A support body is disposable around a threaded bolt of a locking assembly of the tube or pipe clamp. At least one spring element is held by the support body, a compression member being disposed in operative contact with the spring element for compressing the same in a clamp tightening operation. A scale is provided on one of the support body and the compression member for indicating a degree of compression of the spring element and concomitantly a magnitude of compressive force exerted by the compression member and the bolt on the tube or pipe clamp.

Abstract: An apparatus is provided for recording information about an event resulting in application of a force to a body. The apparatus comprises data recording means for recording the information, sensor means for sensing a parameter which enables a predetermined source of force to be distinguished from another, predetermined source of force, and control means responsive to the sensed parameter for controlling the data recording means. The sensor means may comprise a pressure sensor for sensing shockwaves resulting from an explosive force and the resulting signal used to distinguish from other events, such as blunt impacts. The pressure signal may be used to control the storage of acceleration data for injury analysis.

Abstract: An apparatus for testing an angle between first and second legs of a torsion spring includes a board, a limiting block and a pin sandwiching the first leg, a positioning member positioning a main body of the torsion spring with the limiting block, and a test block including a bottom wall slidably contacting the limiting block, and a first sidewall and a second sidewall. Angles between the bottom wall and the first and second sidewalls are respectively minimal and maximal values that equal 180 degrees subtracted by an angle within a qualified range between the first and second legs. The first and second sidewalls is moved toward the second leg in turn. If a bottom end of the first sidewall and a top end of the second sidewall both can contact the second leg, the angle between the first and second legs is qualified. Otherwise, the angle is unqualified.