结论：新品数据说明不了三年后的状态，而使用者用的是三年后的产品

轮椅和其他辅具的检测报告，测的都是新产品。但产品的使用周期是几年，使用者大部分时间用的是已经用过一段时间的产品。

新品与使用几年后的产品，性能差别可能很明显： 轴承阻力增大、织带强度下降、坐垫压实、制动效能降低、电池容量衰减、结构出现旷量。

这些变化多数是渐进的，使用者逐渐适应而不觉得，直到出现明显问题。所以「使用中的产品还安全吗」这个问题，需要数据来回答，而这部分数据通常缺失。

衰减的典型表现

部位 衰减表现 后果
轴承与转动件 阻力增大、旷量 推行费力、续航下降
织带与卡扣 强度下降、保持力衰减 约束失效风险
坐垫 压实、回弹下降 压力分散能力下降
制动 摩擦件磨损、调整变化 制动距离变长
电池 容量衰减、内阻上升 续航缩短
结构 疲劳、松动、腐蚀 强度余量下降
脚垫与轮胎 磨损 防滑性能下降
面料 磨损、老化 破损、卫生问题

「制动距离变长」和「织带强度下降」是安全相关的衰减，而两者都难以从外观判断。

评估的两种途径

途径一：加速耐久试验。 在实验室中用加速的循环和条件模拟长期使用，之后测量性能变化。

优点： 周期可控、条件可重复、可以在产品开发阶段就得到数据。

局限： 加速条件与实际使用的差异、难以模拟全部的环境因素（日照、汗液、清洁剂、意外冲击）。

途径二：实物取样。 从实际使用中的产品取样，测量当前性能。

优点： 反映真实的使用和环境条件、数据可信度高。

局限： 需要能获得使用过的样品、使用历史可能不清楚、样品之间差异大。

两种途径结合效果较好： 用加速试验建立衰减规律，用实物取样验证规律是否成立。

实物取样的做法

样品来源。 机构周转使用的产品、以旧换新回收的产品、维修中的产品、或者与用户协商取得。

使用历史的记录。 使用时长、使用强度、使用环境、维护情况。历史不清楚的样品，数据的解释会受限。

样品数量。 足够反映分散性。

分组。 按使用时长分组，能看出衰减的趋势。

对照。 同型号的新品作为对照。

测试项目。 与新品测试相同的项目，便于直接比较。

「按使用时长分组」能得到衰减曲线，比单个时点的数据有用得多——它能回答「用多久之后性能降到什么程度」。

加速试验的设计

加速的方式。 提高循环频率、增加载荷、加严环境条件。

加速的限度。 不能改变失效机理。比如提高载荷可能引发新品中不会出现的失效模式。

环境因素的纳入。 光照、湿热、清洁剂、汗液模拟液，这些在纯机械循环中不会体现。

中间测量。 在循环过程中的不同时点测量，得到趋势。

与实际的对应。 说明加速试验的循环次数对应实际使用多久。

「环境因素的纳入」是常被省略的部分。 只做机械循环得到的衰减，比实际情况乐观，因为实际使用中材料还在同时经历紫外线、汗液、清洁剂的作用。

数据的用途

确定更换周期。 性能降到什么程度应当更换，对应多长使用时间。

制定检查要点。 哪些部位衰减快、检查时看什么。

支撑产品宣称。 宣称耐用的产品，衰减数据是依据。

指导设计改进。 找出衰减最快的环节并改进。

支持采购决策。 采购方比较不同产品的长期性能。

制定退役判据。 机构管理的产品什么时候应当退役。

「退役判据」对机构客户有实际价值。 机构有大量周转使用的轮椅，什么时候该退役，目前多数凭外观和经验判断，而有数据支撑的判据更可靠。

给使用者的信息

衰减数据可以转化为对使用者有用的信息：

日常检查要点。 具体到看哪里、怎么判断。

更换周期建议。 易损件的更换时机。

性能变化的预期。 比如续航会随电池老化缩短多少。

停用的判据。 出现什么情况应当停止使用。

维护对衰减的影响。 定期维护能延缓哪些衰减。

「停用判据」要具体。 「发现异常应停止使用」这样的表述帮助有限，具体到「制动后车辆仍能被推动」「织带出现起毛或断丝」这类可观察的现象，使用者才能执行。

机构客户的特殊需求

机构周转使用的产品，衰减评估的需求更明确：

周转使用的强度高。 一台轮椅可能一年服务多位使用者，使用强度远高于个人使用。

清洁消毒频繁。 每次更换使用者都要清洁消毒，材料承受的化学作用多。

维护主体明确。 机构有设备管理部门，能执行定期检查。

退役决策需要依据。 什么时候该退役，需要客观判据。

责任更明确。 机构对设备的安全负有责任。

建议机构建立设备台账，记录每台设备的启用时间、使用强度、维护记录、检查结果。有了台账，退役决策就有依据，而不是凭外观判断。

与保修的关系

衰减数据也关系到保修条款的合理性：保修期是否与实际的衰减规律匹配；易损件是否在保修范围内；以及超出保修期后的维护建议。

有衰减数据支撑的保修条款，对双方都更清晰。

我们的做法

做耐久相关的验证时，我们建议在纯机械循环之外加入环境因素——光照、湿热、清洁剂循环 ——因为这些在实际使用中同时作用，只做机械循环的数据偏乐观。

对于有实物样品的委托，我们可以做使用后性能与新品的对比测试，在相同条件下同时测量，差异直接反映衰减幅度。 这类数据在确定更换周期和退役判据时很有用。

如果你需要评估产品的长期性能衰减，或者有使用过的样品需要测试，可以把产品和使用情况发过来一起讨论，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. Test reports for wheelchairs and other assistive products measure new products, while service life runs to years and users spend most of that time with a product that has already been in use. Performance can differ markedly between new and several years old: bearing resistance rises, webbing weakens, cushions compact, braking effectiveness falls, battery capacity declines and structures develop play. Most of these changes are gradual, and users adapt without noticing until something is obviously wrong. The question of whether a product in service is still safe therefore needs data, and that data is usually missing.

Typical manifestations. Bearings and rotating parts show increased resistance and play, making propulsion harder and reducing range. Webbing and buckles lose strength and holding force, risking restraint failure. Cushions compact and lose resilience, reducing pressure distribution. Brakes wear and lose adjustment, lengthening stopping distance. Batteries lose capacity and gain internal resistance, shortening range. Structures fatigue, loosen and corrode, reducing strength margin. Ferrules and tyres wear, reducing grip. And upholstery abrades and ages, leading to damage and hygiene problems. Lengthening braking distance and weakening webbing are the safety-related changes, and neither can be judged by appearance.

Two approaches to assessment. The first is accelerated durability testing, simulating prolonged use in the laboratory through accelerated cycling and conditions, then measuring the change. Its advantages are a controllable schedule, repeatable conditions and data available during development. Its limitations are the difference between accelerated and actual conditions and the difficulty of simulating every environmental factor, including sunlight, perspiration, cleaning agents and accidental impact. The second is sampling products in service and measuring their current performance. Its advantages are that it reflects genuine use and environment and carries high credibility. Its limitations are the need to obtain used samples, uncertain use history and wide variation between samples. Combining the two works well: accelerated testing establishes the decline pattern and field sampling verifies whether the pattern holds.

Sampling from service. Sources include products in institutional rotation, units recovered through trade-in, products in for repair, and units obtained by agreement with users. Record the use history, covering duration, intensity, environment and maintenance; samples with unclear history limit the interpretation of the data. Take enough samples to reflect variation. Group them by duration of use, which reveals the trend. Include a control, being a new unit of the same model. And test the same items as for new products, to allow direct comparison. Grouping by duration produces a decline curve, far more useful than data from a single point, because it answers how far performance has fallen after a given period.

Designing accelerated tests. Acceleration can raise cycling frequency, increase load or intensify environmental conditions. There are limits: acceleration must not change the failure mechanism, and raising load may trigger failure modes that would not occur in service. Environmental factors should be included, covering light, heat and humidity, cleaning agents and simulated perspiration, none of which appear in purely mechanical cycling. Intermediate measurements at points during cycling give the trend. And the correspondence to real use must be stated, explaining what period of service the cycle count represents. Environmental factors are commonly omitted: decline measured by mechanical cycling alone comes out optimistic, because in service the materials are simultaneously exposed to ultraviolet light, perspiration and cleaning agents.

Uses of the data. Setting replacement intervals, defining how far performance may fall and what service period that corresponds to. Defining inspection points, showing which areas decline fastest and what to look at. Supporting product claims, since durability claims need decline data as their basis. Guiding design improvement, identifying the fastest-declining element. Supporting procurement decisions, letting purchasers compare long-term performance. And setting retirement criteria for products under institutional management. Retirement criteria carry real value for institutional customers: institutions hold many chairs in rotation, and when to retire them is currently judged mostly by appearance and experience, whereas data-based criteria are more reliable.

Information for users. Decline data can be turned into useful user information. Daily check points, specific as to where to look and how to judge. Replacement interval recommendations for wear parts. Expected performance change, such as how much range shortens as the battery ages. Criteria for withdrawal from use. And the effect of maintenance, showing which declines regular servicing delays. Make withdrawal criteria concrete: an instruction to stop using the product if anything abnormal is found helps little, while observable descriptions such as the chair still rolling with the brakes applied, or webbing showing fraying or broken fibres, are things users can act on.

How we handle it. For durability work we suggest adding environmental factors to mechanical cycling, covering light exposure, damp heat and cleaning cycles, since all act simultaneously in service and mechanical cycling alone produces optimistic data. Where field samples are available we can test used units against new ones, measuring both under the same conditions at the same time so that the difference reflects the decline directly. That data is valuable in setting replacement intervals and retirement criteria.

Send us the product and its service details and we will work through the assessment. Phone or WeChat: +86 132 4819 8029.