Abstract: A reversible force measuring device that can comprise at least one cavity, at least one load receiving area, and at least one indicating material; wherein the indicating material moves in or out of the at least one cavity as its volume changes to indicate the magnitude and/or direction of the applied loads. A reversible force measuring device that can comprise at least one cavity, at least one load receiving area, and at least one indicating material; a fastener causes the indicating material to move in and out of the at least one cavity to indicate the magnitude and/or direction of the applied loads. A reversible force measuring device comprising at least two independent cavities, at least one load receiving area, and at least one indicating material; wherein the difference in volume changes indicates the force as the indicating material moves in or out of the at least two cavities.

Abstract: An apparatus and method for measuring the tension in bolts, screws, rivets, and other fasteners, is disclosed wherein the deformation of the fastener head is measured (or the end of fastener in such cases as there is not a distinct formed head, for example stud bolts). The deformation generally is an analytic function of the tension in the fastener. The deformation is a continuous two-dimensional distribution over the surface of the fastener head, which allows redundant measurement and therefore more reliable measurement of fastener total axial tension, and also allows in some instances an evaluation of the bending stresses in the fastener from the distortion of the deformation pattern on the head. An advantage of the invention is that the length of the fastener or its temperature need not be known. The measurements can be determined by optical, capacitance, optical imaging, air gauging and piezoresistive techniques.

Abstract: An apparatus and method for measuring the tension in bolts, screws, rivets, and other fasteners, is disclosed wherein the deformation of the fastener head is measured, (or the end of fastener in such cases as there is not a distinct formed head, for example stud bolts). The deformation generally is an analytic function of the tension in the fastener. The deformation is a continuous two-dimensional distribution over the surface of the fastener head, which allows redundant measurement and therefore more reliable measurement of fastener total axial tension, and also allows in some instances an evaluation of the bending stresses in the fastener from the distortion of the deformation pattern on the head. An advantage of the invention is that the length of the fastener or its temperature need not be known. The measurements can be determined by optical, capacitance, optical imaging, air gauging and piezoresistive techniques.