Abstract: A method for reducing vibrations in a drill tubular coupled to a drill bit configured to drill a borehole in a formation includes: constructing a model of a system having the drill tubular, the model having a mass distribution, a stiffness, and/or a damping of the drill tubular; and calculating a plurality of modes using the model. The method also includes increasing an effective damping of the drill tubular for the plurality of modes by modifying at least one of the mass distribution, the stiffness, and the damping of the drill tubular using a predefined damping criterion, wherein the predefined damping criterion includes a ratio, the ratio having a deflection at the drill bit of at least one mode in the plurality and an eigenfrequency of the at least one mode in the plurality, wherein the deflection at the drill bit is raised to a power other than one.

Abstract: A method for reducing vibrations in a drill tubular coupled to a drill bit configured to drill a borehole in a formation includes: constructing a model of a system having the drill tubular, the model having a mass distribution, a stiffness, and/or a damping of the drill tubular; and calculating a plurality of modes using the model. The method also includes increasing an effective damping of the drill tubular for the plurality of modes by modifying at least one of the mass distribution, the stiffness, and the damping of the drill tubular using a predefined damping criterion, wherein the predefined damping criterion includes a ratio, the ratio having a deflection at the drill bit of at least one mode in the plurality and an eigenfrequency of the at least one mode in the plurality, wherein the deflection at the drill bit is raised to a power other than one.

Abstract: A method for reducing drill tubular vibrations includes: constructing a mathematical model the drill tubular having mass distribution, material stiffness and material damping; constructing an equation of motion of the drill tubular in one of a time domain and frequency domain; transforming the equation of motion into a modal domain equation of motion to provide a mode shape of the drill tubular at an eigenfrequency, the mode shape providing an amplitude at a position along the drill tubular; comparing the amplitude at the position along the drill tubular to a threshold amplitude value; modifying at least one of the mass distribution, material stiffness and material damping if the amplitude exceeds the threshold value; and iterating the above step until at least one of the amplitude of the latest mode shape at the position is less than or equal to the threshold amplitude value and a predetermined constraint limits the modifying.

Abstract: Methods of designing an earth-boring tool are described, including calculating one or more performance parameters of the tool based on drilling conditions, a plurality of depth of cut values, and a set of values of other design variables. Methods of enhancing a performance parameter in the design of an earth-boring tool are also described, including calculating the performance parameter based at least partially on a plurality of depth of cut values and a first set of values of other design variables, calculating the performance parameter based at least partially on a second set of values of the other design variables different than the first set, and comparing the calculated performance parameters to determine which of the first and the second set is closer to a target range or value across a range of the plurality of depths of cut. Related methods of forming an earth-boring tool are also described.

Abstract: A method for reducing drill tubular vibrations includes: constructing a mathematical model the drill tubular having mass distribution, material stiffness and material damping; constructing an equation of motion of the drill tubular in one of a time domain and frequency domain; transforming the equation of motion into a modal domain equation of motion to provide a mode shape of the drill tubular at an eigenfrequency, the mode shape providing an amplitude at a position along the drill tubular; comparing the amplitude at the position along the drill tubular to a threshold amplitude value; modifying at least one of the mass distribution, material stiffness and material damping if the amplitude exceeds the threshold value; and iterating the above step until at least one of the amplitude of the latest mode shape at the position is less than or equal to the threshold amplitude value and a predetermined constraint limits the modifying.

Abstract: Methods of designing an earth-boring tool are described, including calculating one or more performance parameters based on drilling conditions, a plurality of wear state values, and a set of values of other design variables. Methods of enhancing a performance parameter in the design of an earth-boring tool are also described, including calculating the performance parameter based at least partially on a plurality of wear state values and a first set of values of other design variables, calculating the performance parameter based at least partially on the plurality of wear state values and a second set of values of design variables different than the first set, and comparing the calculated performance parameters to determine which of the first and the second set is closer to a target range or value across a range of the plurality of wear state values. Related methods of forming an earth-boring tool are also described.

Abstract: Methods of designing an earth-boring tool are described, including calculating one or more performance parameters of the tool based on drilling conditions, a plurality of depth of cut values, and a set of values of other design variables. Methods of enhancing a performance parameter in the design of an earth-boring tool are also described, including calculating the performance parameter based at least partially on a plurality of depth of cut values and a first set of values of other design variables, calculating the performance parameter based at least partially on a second set of values of the other design variables different than the first set, and comparing the calculated performance parameters to determine which of the first and the second set is closer to a target range or value across a range of the plurality of depths of cut. Related methods of forming an earth-boring tool are also described.

Abstract: Methods of designing an earth-boring tool are described, including calculating one or more performance parameters of the tool based on drilling conditions, a plurality of depth of cut values, and a set of values of other design variables. Methods of enhancing a performance parameter in the design of an earth-boring tool are also described, including calculating the performance parameter based at least partially on a plurality of depth of cut values and a first set of values of other design variables, calculating the performance parameter based at least partially on a second set of values of the other design variables different than the first set, and comparing the calculated performance parameters to determine which of the first and the second set is closer to a target range or value across a range of the plurality of depths of cut. Related methods of forming an earth-boring tool are also described.

Abstract: Methods of designing an earth-boring tool are described, including calculating one or more performance parameters based on drilling conditions, a plurality of wear state values, and a set of values of other design variables. Methods of enhancing a performance parameter in the design of an earth-boring tool are also described, including calculating the performance parameter based at least partially on a plurality of wear state values and a first set of values of other design variables, calculating the performance parameter based at least partially on the plurality of wear state values and a second set of values of design variables different than the first set, and comparing the calculated performance parameters to determine which of the first and the second set is closer to a target range or value across a range of the plurality of wear state values. Related methods of forming an earth-boring tool are also described.

Abstract: A method of making a drill bit for drilling subterranean formations includes forming a first blade having a shape and configuration defined by one or more first parameters and forming a second blade having a shape and configuration defined by one or more second parameters. One of the first parameters is different than one of the second parameters.