《材料力学》课程PPT教学课件（双语版）第十六章 材料力学性能的进一步研究

Mechanics of materials

Mechanics of Materials

材料力学低的远一少研究

CHAPTER16 FURTHER RESEARCH ON MECHANICAL PROPERTIES OF MATERIALS §16-1 SUMMARY D816-2 EFFECTS OF THE STRAIN RATE AND STRESS RATE ON MECHANICAL PROPERTIES OF MATERIALS 」§163 EFFECTS OF TEMPERATURE ON MECHANICAL PROPERTIES OF MATERIALS S $16-4 EFFECTS OF TEMPERATURE AND TIME ON MECHANICAL PROPERTIES OF MATERIALS CREEP AND RELAXATION $16-5 MECHANICAL PROPERTIES OF MATERIALS UNDER IMPACT LOADS. IMPACT TOUGHNESS. TRANSITON TEMPERATURE

CHAPTER16 FURTHER RESEARCH ON MECHANICAL PROPERTIES OF MATERIALS §16–1 SUMMARY §16–2 EFFECTS OF THE STRAIN RATE AND STRESS RATE ON MECHANICAL PROPERTIES OF MATERIALS §16–3 EFFECTS OF TEMPERATURE ON MECHANICAL PROPERTIES OF MATERIALS §16–4 EFFECTS OF TEMPERATURE AND TIME ON MECHANICAL PROPERTIES OF MATERIALS ·CREEPAND RELAXATION §16–5 MECHANICAL PROPERTIES OF MATERIALS UNDER IMPACT LOADS · IMPACT TOUGHNESS · TRANSITON TEMPERATURE

第十六章材料力学性能的进一步研究 §16-1概述 §16-2应变速率及应力速率对材料力学性能的影响 §16-3温度对材料力学性能的影响 §164温度与时间对材料力学性能的影响·蠕变与松弛 §16-5冲击荷载下材料的力学性能·冲击韧度转变温度

第十六章 材料力学性能的进一步研究 §16–1 概述 §16–2 应变速率及应力速率对材料力学性能的影响 §16–3 温度对材料力学性能的影响 §16–4 温度与时间对材料力学性能的影响 · 蠕变与松弛 §16–5 冲击荷载下材料的力学性能 ·冲击韧度 ·转变温度

8 16-1 SUMMARY The mechanical properties of materials at high temperature, in static loading(by quasi static test), tension and compression are introduced in the above chapter 1. Real structures or members usually work under complex conditions. For example, the working temperature of some petroleum chemical equipments is very slow, and the working temperature of some internal-combustion engines or gas turbines is very high the blades of the steam turbines are always subjected to large centrifugal forces, the prestressed steel bars or wires in the prestressed steel-bar reinforced concrete always work under high pre-tensile stresses at normal temperatures for periods of long time; the bridge beams, crane beams and most motive machines are often subjected to the loads varying alternately with time; the wind- driven machinery pneumatic hammers and conventional weapons are often subjected to impact loads repeatly and etc. So the effects of these factors on mechanical properties of materials are needed to be considered in the strength calculation

§16–1 SUMMARY The mechanical properties of materials at high temperature, in static loading(by quasi- static test), tension and compression are introduced in the above chapter 1. Real structures or members usually work under complex conditions. For example, the working temperature of some petroleum chemical equipments is very slow, and the working temperature of some internal-combustion engines or gas turbines is very high; the blades of the steam turbines are always subjected to large centrifugal forces; the prestressed steel bars or wires in the prestressed steel-bar reinforced concrete always work under high pre-tensile stresses at normal temperatures for periods of long time; the bridge beams, crane beams and most motive machines are often subjected to the loads varying alternately with time; the wind- driven machinery pneumatic hammers and conventional weapons are often subjected to impact loads repeatly and etc. So the effects of these factors on mechanical properties of materials are needed to be considered in the strength calculation

§16-1概述 前面第一章中介绍了材料在高温、静载(用准静态试验)拉 伸、压缩时的力学性能。实际的结构物或构件往往是在比较复 杂的条件下工作的,例如,石油化工设备中有些机器的工作温度 很低,而内燃机或燃气轮机的工作温度很高;汽轮机的叶片在高 温下长期受很大的离心力作用;预应力钢筋混凝土中的预应力钢 筋或钢丝束则在常温下长期在很高的预拉应力下工作;桥梁、吊 车梁以及绝大多数的动力机械所受荷载多是随时间交替变化的; 风动机械、气锤、常规武器则经常受到冲击载荷的反复作用,等 等。因此在强度计算时常需考虑这些因素对材料力学性能的影响

§16–1 概述 前面第一章中介绍了材料在高温、静载（用准静态试验）拉 伸、压缩时的力学性能。 实际的结构物或构件往往是在比较复 杂的条件下工作的，例如，石油化工设备中有些机器的工作温度 很低，而内燃机或燃气轮机的工作温度很高；汽轮机的叶片在高 温下长期受很大的离心力作用；预应力钢筋混凝土中的预应力钢 筋或钢丝束则在常温下长期在很高的预拉应力下工作；桥梁、吊 车梁以及绝大多数的动力机械所受荷载多是随时间交替变化的； 风动机械、气锤、常规武器则经常受到冲击载荷的反复作用，等 等。因此在强度计算时常需考虑这些因素对材料力学性能的影响

816-2 EFFECTS OF THE STRAIN RATE AND STRESS RATE ON MECHNICAL PROPERTIES OF MATERIALS 1\ Effects of the strain rate on mechanical properties of materials Experimental results prove that mechanical properties of d materials are affected obviously by the strain rate &<=3mm/mm/s dt when it exceeds 3mm/mm/s. The load that makes the strain rate i exceed 3mm/mm/s is customly called dynamic load

Experimental results prove that mechanical properties of materials are affected obviously by the strain rate §16–2 EFFECTS OF THE STRAIN RATE AND STRESS RATE ON MECHNICAL PROPERTIES OF MATERIALS 1、Effects of the strain rate on mechanical properties of materials 3mm/mm/s d d   t    3mm/mm/s when it exceeds . The load that makes the strain rate exceed is customly called dynamic load. 3mm/mm/s

§162应变速率及应力速率对材料力学性能的影响 应变速率对材料力学性能的影响 试验结果指出,在应变速率超过8x=3mm/mm/s以后, dt 材料的力学性能就显著地受到应变速率的影响。使构件的应 变速率超过3mm/m的荷载,习惯上称为动荷载

§16–2 应变速率及应力速率对材料力学性能的影响 试验结果指出，在应变速率超过 以后， 材料的力学性能就显著地受到应变速率的影响。使构件的应 变速率 超过 的荷载，习惯上称为动荷载。 3mm/mm/s d d   t    3mm/mm/s 一、应变速率对材料力学性能的影响

Dynamic load 320 2 300 280 260 static load 240 220 e 200 O 020406080100 S (MPa/s) Low-carbon stee Relationship between the stress rate and the yield limit 2\ Effects of the stress rate on mechanical properties of materials When we test the yield limit of a material in the lab the loading rate is also the stress rate in the sample

Relationship between the stress rate and the yield limit 0 20 40 60 80 100 320 300 280 260 240 220 200 s s ( M P a ) s (MPa/s) · O s e 1 static load 2 2、Effects of the stress rate on mechanical properties of materials When we test the yield limit of a material in the lab, the loading rate is also the stress rate in the sample. Low-carbon steel Dynamic load

320 2 动荷载 300 280 260 静荷载 2240 220 e 200 O 020406080100 低碳钢 S (MPa/s) 应力速率与屈服极限的关系 应力速率对材料力学性能的影响 在实验室内测定材料的屈服极限时,加载速率也就是试 样中的应力速率

应力速率与屈服极限的关系 0 20 40 60 80 100 320 300 280 260 240 220 200 s s ( M P a ) s (MPa/s) · 低碳钢 O s e 1 静荷载 2 动荷载 二、应力速率对材料力学性能的影响 在实验室内测定材料的屈服极限时，加载速率也就是试 样中的应力速率