应力应变，哪个才是更为基础的物理量（4）

应力应变讨论，接着上次，提出更理性的思考，欢迎讨论哟~...



Interesting debate：

What is its parallel on the stress side?

Like Displacement -> Deformation on the strain side, we have Force -> Pressure (stress) on the stress side. And if we consider instantaneous (true) strain measure,we can eliminate the multi-valued functions even if we plot strain in Y-axis (I guess, you can shed light into this). Also Force (and hence stress) we measure is with respect to some reference value and it is not exact. But strain measure is exact.

有趣的辩论：与位移-形变一侧相对应的是什么呢？

就像应变这一侧中位移到形变的概念关系一样，在应力一侧，我们有力到压力（或称为应力）的概念。而且，考虑到在瞬时（真）应变的测量中，如果我们将应变表示在y轴上，那么我们将可以得到一个单值函数（我猜你可以实现这个）。同样地，在力（进而是应力）的测量中，我们是基于某一个参考值，所以力的测量并非准确的，但是应变的测量却与之相反，是准确的。

But I go with the Strain (or deformation). Because we could explain the linear behavior of materials with Stress (S-N curves), and both linear and non linear with Strain life calculations.

但是我支持应变（或者称为变形）是更加基本的物理量这一观点，因为我们可以通过应力疲劳寿命曲线来解释应力作用下材料的线性行为，以及应力疲劳计算中的材料的线性和非线性行为。

When we consider Force as an action that causes deformation, we are carving out a system to cover only the specific entity we wanted to analyze, and think that force is primary. But energy is needed and pre-exist before we could actually think of force.

当我们认为力是产生变形的条件时，我们构建的体系（认为力是主要的）已经限制了这个体系所适用的对象。但是在我们认知“力”的时候，我们需要提前明确能量的概念。

One can store energy (in a cantilever beam) by pushing it down, as energy is
transferred from us, and when we see it, we consider only that force as the
action, and deformation as the result. When we release it, we have the
deformation as the action, force (if any thing restraining or connected to) is
the result. But according to Mathematicians, we have energy defined in terms of stress and strain, and both may be independent variables. And zero is not null.

对于悬臂梁，能量可以通过我们对它施加力这一方式来储存，此时能量从我们转移到了悬臂梁。从表象上来看，该过程中仅仅只有力产生了作用，而变形是力作用的结果。当我们释力时，变形则成为了作用，力（比如当有约束或者关联）反而成立变形作用的结果。但是根据数学家们的观点，我们是基于应力与应变来定义能量的，而且应力和应变是相互独立的变量，而且能量的零点存在。

One question I would like to ask others is that, I heard about stress singularities, but did not come across strain singularities -- which means we take strain as a fundamental measure (leaving out energy from the discussion).

我还有一个问题想问大家，我听说过所谓的应力奇点，但没有听说过应变的奇点，这是否意味着应变才是更加基础的物理量（撇开能量不谈）？

翻译编辑：缪昌旭 唐一廷 阿曦Arish：D

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