结论：这两个部件的实际受力方式，比试验规定的更复杂
扶手和脚踏在试验中通常承受规定方向的静载荷。但在实际使用里，它们承受的是转移过程中的复合载荷：使用者撑着扶手起身、护理者扳着扶手挪动轮椅、使用者踩着脚踏站起来。
这些动作的受力方向、大小和作用时长都与试验条件不同。理解这个差别，才能判断试验通过之后产品在真实使用中是否可靠。
扶手的失效模式
| 受力方向 | 对应的使用动作 | 典型失效 |
|---|---|---|
| 向下压 | 使用者撑扶手起身 | 扶手弯曲、安装点变形 |
| 向外掰 | 侧向转移时借力 | 安装点松动、连接件断裂 |
| 向上提 | 护理者提起轮椅 | 扶手脱出、锁定机构失效 |
| 向后拉 | 推动轮椅时握持 | 后安装点受拉失效 |
| 扭转 | 单手借力起身 | 扶手管转动、固定螺栓松脱 |
第三行是风险较高的一项。 可拆卸扶手如果锁定不可靠，护理者提扶手搬动轮椅时扶手脱出，轮椅落下，可能造成伤害。这个使用方式虽然不在设计预期内，但实际中很常见。
第五行则常被忽略。 单手撑扶手起身时，扶手承受的不只是向下的力，还有扭转。管状扶手如果只靠一个夹紧点固定，容易在这个工况下转动。
脚踏的失效模式
脚踏的受力场景与扶手不同：
向下踩踏。 使用者踩着脚踏站起，这时脚踏承受远超正常搁脚的载荷。这是脚踏失效最常见的场景。
前向冲击。 轮椅前行撞到障碍，脚踏首当其冲。这种工况在跌落和冲击试验中部分覆盖。
翻转机构受力。 多数脚踏可翻起以便转移，翻转机构在反复使用中磨损，间隙增大后承载能力下降。
拆装接口。 可拆卸脚踏的插接结构在反复拆装后配合变松，可能在承载时脱出。
可拆卸结构的额外问题
扶手和脚踏越来越多采用可拆卸设计，方便转移和运输。这带来两类新的考察点：
一是锁定可靠性。 锁定机构要在使用中不会意外解除。考察方式包括施加各方向载荷时锁定是否保持、以及误操作是否可能导致解锁。
二是反复拆装后的性能保持。 新件装配紧密，拆装几百次之后配合可能变松。这一点在出厂检验里测不出来，需要通过耐久试验考察。 实际售后中因为配合松动导致的问题，相当一部分源于此。
与说明书的配合
试验能覆盖的使用方式是有限的，超出部分应当在说明书中处理。
比较重要的几条提示包括：扶手能否作为提起轮椅的受力点；脚踏能否承受站立；可拆卸部件的正确装配方式与确认方法；定期检查锁定机构的建议。
这些提示的依据应当是试验数据。 如果扶手确实不能用于提起轮椅，说明书要明确写出来并给出正确的搬运方式；如果试验证明可以，则不必限制。凭感觉写限制，既可能限制过度影响使用，也可能遗漏真正的风险。
设计上的应对
针对上面的失效模式，可行的改进方向包括：
扶手采用两点或多点固定，避免单点夹紧导致的转动；安装点做局部补强，因为失效常发生在安装点而非部件本身；锁定机构设置防误解锁特征；可拆卸接口考虑磨损后的补偿方式，比如可调的夹紧力；脚踏按站立载荷而不是搁脚载荷设计。
最后一条的实际意义较大。 使用者踩脚踏站起是普遍行为，按搁脚载荷设计的脚踏在这个工况下容易失效。
送检时的建议
委托时把这几件事说清楚：扶手和脚踏是固定式还是可拆卸；可拆卸的锁定方式是什么；产品是否允许用扶手提起、是否允许踩脚踏站立；如果不允许，说明书是否已有相应提示。
如果产品定位涉及较多转移操作（比如面向护理机构），建议在摸底阶段补做几个方向的受力和拆装耐久，覆盖标准之外但实际高发的工况。
使用方式调查的价值
扶手和脚踏的失效多数源于超出设计预期的使用方式。所以在设计阶段做一次使用方式调查，价值很高。
调查的内容包括：使用者通常怎么借力起身、护理者怎么搬动轮椅、转移时手脚分别放在哪里、有没有把轮椅当作其他用途的情况。这些信息可以来自售后反馈、护理机构走访，或者直接观察。
调查结果应当转化成设计输入和试验条件。 如果调查发现护理者普遍用扶手提起轮椅，那么这个工况就应当纳入验证，而不是仅在说明书里禁止——禁止了但大家还是这么做，风险并没有消除。
儿童产品的特殊考虑
儿童轮椅上，扶手和脚踏的受力场景与成人产品不同。照护者的介入更多，抱起、搬动、调整姿势的频次更高，而这些动作常常借力于扶手。
同时儿童产品的尺寸小、部件轻巧，设计上容易偏向轻量化而牺牲承载余量。载荷按儿童体重设计，但实际承受的可能是成年照护者的力。 这个差距在设计时要考虑进去。
部件互换带来的问题
扶手和脚踏常有多个规格可选，使用者或经销商可能自行更换。这带来一个风险：非原厂或非配套部件的承载能力未经验证。
对此可行的做法是在接口设计上做区分，使不匹配的部件装不上；或者在说明书中明确可用的配件清单与更换要求。如果产品允许更换，那么可选配件也应当纳入验证范围，而不是只验证出厂标配。
我们的做法
做这两项时，我们会记录失效发生的位置——是部件本身、安装点，还是锁定机构。三者对应的整改方向不同，只给一个不合格结论没有指导价值。
对于可拆卸结构，建议把拆装耐久作为补充项目。这一项不在常规清单里，但它对应的是实际售后中较高发的问题，做一次的成本远低于批量出现松动后的处理成本。
有需要可以把扶手脚踏的结构图和锁定方式说明发过来一起看，或者直接联系：132 4819 8029。检测能力见服务介绍，产品分类见手动轮椅检测与电动轮椅检测，标准信息见标准查询。
English version
Conclusion. Armrests and footrests are tested under specified static loads in defined directions. In service they carry combined loading during transfers: a user pushing down on an armrest to stand, a carer pulling an armrest to reposition the chair, a user standing on a footrest. Direction, magnitude and duration all differ from test conditions, and understanding that gap is what tells you whether a passing product is reliable in use.
Armrest failure modes. Downward loading, as a user pushes up to stand, produces bending of the armrest or deformation at the mounting. Outward loading during a lateral transfer loosens the mounting or breaks connecting parts. Upward loading, when a carer lifts the chair by the armrests, can pull the armrest out or defeat the locking mechanism. Rearward loading while pushing stresses the rear mounting in tension. Torsional loading, when a user pushes up with one hand, can rotate a tubular armrest or loosen its clamping bolt.
The upward case carries the most risk. Where a removable armrest does not lock reliably, lifting the chair by it can release the armrest and drop the chair. This is outside the design intent but common in practice. The torsional case is the most overlooked: single-handed pushing applies twist as well as downward force, and a tube secured by a single clamp point rotates readily.
Footrest failure modes. Standing on a footrest imposes loading far beyond that of simply resting the feet, and is the most common failure scenario. Forward impact when the chair strikes an obstacle loads the footrest first, partly covered by drop and impact testing. Flip-up mechanisms wear with repeated use and lose capacity as clearance increases. Removable footrest interfaces loosen after repeated fitting and removal and may disengage under load.
Removable designs. These raise two additional considerations. Locking reliability requires that the mechanism holds under loading from all directions and cannot be released by foreseeable misuse. Retention of performance after repeated removal and refitting matters because a new part fits tightly while the same part after several hundred cycles may not; this cannot be detected in batch release testing and needs an endurance assessment. A significant share of field problems with loose fit originate here.
Working with the instructions for use. Testing covers a limited set of use patterns and the remainder must be handled in the instructions: whether armrests may be used to lift the chair, whether footrests will support standing, how removable parts are correctly fitted and verified, and a recommendation to check locking mechanisms periodically. These statements should rest on test data. Writing restrictions from intuition risks both over-restricting normal use and missing a real hazard.
Design responses. Secure armrests at two or more points rather than a single clamp. Reinforce mountings locally, since failure commonly occurs there rather than in the component. Design locking mechanisms against inadvertent release. Allow for wear at removable interfaces, for example through adjustable clamping. Design footrests for standing loads rather than resting loads, which matters because standing on footrests is widespread behaviour.
When commissioning testing. State whether armrests and footrests are fixed or removable, how removable parts lock, whether the product permits lifting by the armrests or standing on the footrests, and whether the instructions already carry the corresponding statements. Products aimed at care settings, where transfers are frequent, benefit from supplementary multi-direction loading and fit-and-remove endurance during preliminary testing.
How we handle it. We record where failure occurred, in the component, at the mounting or in the locking mechanism, since the three imply different remedies. For removable designs we suggest adding fit-and-remove endurance as a supplementary item; it is not on the standard list but corresponds to a frequent field problem, and running it once costs far less than handling loosening across a production run.
Send us the structural drawings and a description of the locking arrangement. Phone or WeChat: +86 132 4819 8029.