Hardness. Measure of a material’s resistance to localized plastic deformation. Most hardness tests involve indentation, but hardness may be reported as resistance to scratching (file test), or rebound of a projectile bounced off the material (scleroscope hardness). Some common measures of indentation hardness are Brinell hardness number, Rock well hardness number, ASTM hardness number, diamond pyramid hardness number, durometer hardness, Knoop harness and Pfund hardness number. A table relating various type of hardness values of metals is given in ASTM E-140. Hardness often is a good indication of tensile and wear properties of a material.

硬度。是指测量材料对局部塑性变形的抵抗能力。大多数硬度测试均会导致压痕，但硬度可记录为耐划伤(锉刀试验)，或弹丸反弹材料(肖式硬度)。常用的压痕硬度测量方法有布氏硬度值、洛氏硬度值、ASTM硬度值、金刚石锥体硬度值、硬度计硬度值、努氏硬度值和Pfund硬度值。ASTM E-140中给出了关于各种金属硬度值的表格。此外，硬度通常是材料的拉伸和磨损性能的良好指标。

Heat distortion point. Temperature at which a standard plastic test bar deflects 0.010 in. under a maximum fiber stress of 66 or 264 psi. (ASTM D-648). An alternate term is deflection temperature.

热变形点。是指当最大纤维应力为66或264 psi时，标准塑料测试棒挠曲0.010英寸时的温度。(ASTM D-648)。它又称为挠曲温度。

Heat distortion temperature. An alternate term for deflection temperature.

热变形温度。挠曲温度的另一种术语。

Hooke’s law. Stress is directly proportional to strain. Hooke’s law assumes perfectly elastic behavior. It does not take into account plastic or dynamic loss properties.

胡克定律。即应力与应变成正比。胡克定律假定完全弹性性能。它不考虑塑性或动态耗损特性。

Hoop stress. Circumferential stress in a cylinder subjected to internal hydrostatic pressure. For thin wall cylinders it can be calculated by Barlow’s formula: S = PD/2t where S is hoop stress in psi; P, applied pressure in psi; D, cylinder o.d. in in.; and t, wall thickness in in. Barlow’s formula does not hold for thick-wall cylinders where stress varies across wall thickness.

周向应力。受到内部静水压力作用的圆柱体的周向应力。对于薄壁圆圆柱体，可采用Barlow公式计算:S = PD/2t，其中S为周向应力，单位为psi;P，表示施加压力，单位为psi;D，表示气缸外部直径，单位为in.;t，表示壁厚，单位为in.。但Barlow的公式不适用于应力随壁厚变化的厚壁圆柱体。

Hot hardness. Measure of hardness at elevated temperature. Often it is determined by heating a specimen, removing it from the oven and testing it with standard hardness testers. However, this is not a true indication of hardness at temperature because the surface cools quickly after removal from the oven and surface properties are critical in hardness testing. Several methods and apparatus for hot hardness testing are described in “Property Measurements at High Temperatures,” W. D. Kingrey, John Wiley & Sons, Inc.

热硬度。是指在高温下测量的硬度。通常是通过加热某个试样，将其从烤箱中取出并采用标准硬度测试仪测试来确定。然而，这并不是硬度在温度下的真实指标，因为其表面在从烤箱中取出后会迅速冷却，而表面性能在硬度测试中又至关重要。其中W. D. Kingrey的《高温下的性能测量》(约翰威立国际出版公司出版)中介绍了几种用于热硬度测试的方法和设备。